This invention relates to the art of pipe wrenches and more particularly, to improvements in pivoting jaw pipe wrenches.
Pivoting jaw pipe wrenches are known as shown, for example, in U.S. Pat. No. 2,028,406 to Mead and U.S. Pat. No. 2,559,973 to Kunz. Such wrenches typically include a handle having a fixed toothed jaw at one end thereof and a toothed jaw member pivotally mounted on the one end for displacement toward and away from the fixed jaw. The pivotal jaw member has teeth thereon which are cooperable with the teeth on the fixed jaw to grip a pipe or other workpiece therebetween, and the pivotal jaw is spring biased toward the fixed jaw to provide a closing force against the pipe or workpiece therebetween. In the Mead patent, the teeth on the fixed jaw extend in an arcuate path therealong and the pivotal jaw is provided with two sets of teeth which are at an obtuse angle relative to one another and which are spaced apart along the jaw. Each set of teeth on the pivotal jaw is cooperable with a different portion of the teeth on the fixed jaw to grip a square or round object therebetween. In the Kunz patent, the teeth on the fixed jaw extend along an arcuate face thereof and the pivotal jaw comprises a pair of legs at substantially right angles to one another and provided with corresponding sets of teeth. A pipe to be gripped by the wrench is cradled between the legs of the pivotal jaw and is urged against the fixed jaw to provide three point contact between the wrench jaws and pipe.
Pivoting jaw wrenches are desirable in that they are quickly applied to a workpiece to be gripped and turned, such as a pipe or pipe coupling and are self-adjusting to the size of the workpiece. However, the gripping capability of such wrenches is compromised when a large range of pipe sizes are required to be gripped while limiting the rotational swing of the pivotal jaw to 90° to facilitate operability of the wrench. In this respect, a large range of pipe sizes and the limitation of a 90° swing of the pivotal jaw results in undesirable slippage between the wrench and pipe in connection with the turning of larger sizes of pipe such as 1½ inches to 2 inches and larger diameter pipe. Further in this respect, a line from the pivot axis of the pivotal jaw to a given point on the arcuate jaw face and from the latter point through the vertex between the sets of teeth on the pivotal jaw provides a camming angle for a given diameter pipe and, in many pivoting jaw wrenches heretofore provided, the camming angle becomes unfavorable on the larger sizes of pipes which results in inefficient gripping performance, slippage and potential damage to the workpiece as well as the teeth on the jaws of the wrench.